This invention relates to a regeneration method of catalyst. More particularly, it relates to a method for the regeneration of a solid acid catalyst which is used when various cyclic alcohols useful as intermediate raw materials are produced by hydrating cyclic olefins in a liquid phase.
It is known that a cyclic alcohol such as cyclohexanol is produced by effecting hydration of a cyclic olefin such as cyclohexene in a liquid phase in the present of a solid acid catalyst such as zeolite. For example, when zeolite is used as the catalyst and cyclohexene is used as the raw material, a water phase containing microgranular zeolite and an oil phase containing the raw material cyclohexene are allowed to react with each other under a suspended condition in a stirring tank, and most of the thus formed cyclohexanol is distributed in said oil phase.
When such a reaction is considered from the viewpoint of mass transfer, there is a phenomenon in which cyclohexene in the oil phase is transferred to zeolite via water in the water phase and undergoes hydration and then the thus formed cyclohexanol is transferred to the oil phase through the opposite path. However, this reaction causes a problem of accumulating by-products in zeolite.
In the aforementioned hydration of olefin in a liquid phase by a solid acid catalyst such as zeolite, organic substances are accumulated mainly on the catalyst with the progress of reaction, so that the activity of catalyst is gradually reduced. Examples of known methods for regenerating such a catalyst with reduced activity include a method in which it is heat-treated at a high temperature in the presence of molecular oxygen (JP-A-61-234946; the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and a method in which it is treated with a liquid phase oxidizing agent (JP-A-61-234945, JP-A-3-224633). However, the conventional regeneration methods have a problem in that recovery of the catalytic activity is insufficient. That is, though almost satisfactory recovery of the activity can be achieved at the initial stage of regeneration, reduction of the activity becomes significant as the regeneration is repeated.
The conventionally known techniques are merely aiming at the regeneration method itself for how to recover the catalytic activity and are not examined by connecting the activity recovery of catalyst with the improvement of the reaction process itself.
Regarding the aforementioned reaction process, JP-A-6-239780 describes that, in the hydration of a cyclic olefin using zeolite, a water phase and an oil phase are subjected to oil water separation inside or outside of a reactor, and the oil phase containing the reaction product is drawn out. However, the above known reference does not describe about temperature of the oil water separation or about regeneration of the separated catalyst.
The inventors of the present invention have conducted intensive studies on a catalyst regeneration method which causes extremely small reduction of catalyst activity even after repeated regeneration and use of a catalyst and found as a result of the efforts that, when a regeneration method having a step of effecting phase separation of an oil phase containing a cyclic olefin and its reaction product such as an alcohol and a water phase containing a catalyst, from the reaction mixture at a temperature of 40xc2x0 C. or more is employed, the catalyst can be regenerated with higher efficiency than those of the conventional methods and the catalytic activity can be maintained at a high level even after the use of the catalyst for a prolonged period of time by repeating its regeneration, thus resulting in the accomplishment of the present invention.
Accordingly, the present invention relates to a method for regenerating a cyclic olefin hydration catalyst, in which a solid acid catalyst is regenerated after its use in a hydration reaction of a cyclic olefin by mixing a water phase containing the solid acid catalyst and an oil phase containing the cyclic olefin and thereby effecting the reaction, which comprises separating the reaction solution into oil phase and water phase at a temperature of 40xc2x0 C. or more and subsequently subjecting at least a portion of the solid acid catalyst in said separated water phase to a regeneration treatment.
The present invention also relates to a method for producing a cyclic alcohol by carrying out continuous reaction of a cyclic olefin with water, which comprises the steps of:
(1) forming a reaction mixture by mixing a water phase containing a solid acid catalyst with an oil phase containing a cyclic olefin and a cyclic alcohol;
(2) drawing out the reaction mixture continuously from a reactor and carrying out oil water separation at a temperature of 40xc2x0 C. or more; and
(3) subjecting at least a portion of the solid acid catalyst in the water phase obtained by the oil water separation to a regeneration treatment.
The present invention also relates to a method for producing a cyclic alcohol by carrying out continuous reaction of a cyclic olefin with water, which comprises the steps of:
(1) forming a reaction mixture by mixing a water phase containing a solid acid catalyst with an oil phase containing a cyclic olefin and a cyclic alcohol in a reactor having an oil water separation function inside thereof;
(2) drawing out the oil phase separated in the reactor, continuously from the reactor;
(3) separately from the oil phase drawing of step (2), drawing out the reaction mixture continuously from the reactor and carrying out oil water separation at a temperature of 40xc2x0 C. or more; and
(4) subjecting at least a portion of the solid acid catalyst in the water phase obtained by the oil water separation of step (3) to a regeneration treatment.
The present invention also relates to a method for producing a cyclic alcohol by carrying out continuous reaction of a cyclic olefin with water, which comprises the steps of:
(1) mixing a water phase containing a solid acid catalyst with an oil phase containing a cyclic olefin and a cyclic alcohol, in a reactor having an oil water separation function inside thereof;
(2) drawing out the oil phase separated at a temperature of 40xc2x0 C. or more in the reactor, continuously from the reactor;
(3) drawing out from the reactor, the water phase containing oil phase components, crudely separated at a temperature of 40xc2x0 C. or more in the reactor;
(4) further carrying out oil water separation of the oil phase component-containing water phase drawn out from the reactor in step (3), at a temperature of 40xc2x0 C. or more; and
(5) subjecting at least a portion of the solid acid catalyst in the water phase obtained by the oil water separation of step (4), to a regeneration treatment.